RELATIVES OF THE FERNS 59 



very similar situations to that which is favoured 

 by the giant species. Sowerby tells us that 

 the first-mentioned plant is a very active agent 

 in the changing of pools into swampy places. 

 As soon as the surface water has departed 

 the plant abandons the position for a wetter 

 situation. In both these species the spore- 

 bearing cones are produced on the end of 

 the green branched shoots, and thus the fertil- 

 ising dust is not matured until well into the 

 summer. 



The most graceful of all the horsetails — E. 

 sylvaticum — is usually to be found in shaded 

 places where there is a fair amount of moisture. 

 It is rarely more than about fifteen inches in 

 height, and its slender stem is hardly strong 

 enough to maintain it in an upright position ; a 

 fact which rather adds to the general appearance 

 of the plant. A singular feature of this species is 

 that its fertile shoots at first exactly resemble 

 those of the common Field Horsetail. They 

 do not, however, die down when their special 

 business is accomplished, for afterwards they 

 produce green lateral shoots, so that finally it 

 may be difficult to distinguish them from the 

 non-fertile stems. 



